"The overall objective of the proposal is to improve performance of polymer matrix composite materials for cryogenic tank applications. The specific objectives of the program are:1. Determine the effect of cryogenic exposure on PMCs, particularly on the interphase region.2. Examine failed composite cryogenic tanks at the nanometer-level and higher to understand failure mechanisms.3. Develop protocols to determine appropriate polymer curing to achieve better PMC performance in cryogenic tank applications. The technology transfer research detailed in this proposal will improve the performance of polymer matrix composites with respect to producibility and cycle life. With more information concerning permeability, PMC cryogenic tanks will find use inairborne laser systems, although this is not expected to be a high volume application as only 7 airborne laser systems are expected to be in service at any one time. The composite cryogenic tanks are also necessary for the development of 2nd and 3rdgeneration space vehicles, particularly reusable launch vehicles. Lightweight composite cryogenic tanks are required to reduce the launch cost from >$10,000/ lb. payload to